There is provided a hydraulic circuit of a work machine enabled to correspond to required flow rates for various attachment tools by controlling a tool control valve, a first confluence valve, and a second confluence valve of the work machine by operating a solenoid selector valve of a selecting means and thereby selectively feeding a flow rate of a first pump, a confluent flow rate of first and second pumps, or a confluent flow rate of first, second, and third pumps (see Japanese Laid-Open Patent Publication No. 2004-245262, e.g., Page 5, FIG. 1).
As shown in FIG. 9, for a work machine A, on a lower structure 1 to be driven by left and right travel motors 1tr, an upper structure 2 is provided so as to be rotatable by a swing motor 2sw, and work equipment 3 is mounted on this upper structure 2. For the work equipment 3, pivotally supported on the upper structure 2 is a boom 4 to be pivoted by a boom cylinder 4bm, pivotally supported on a front end portion of this boom 4 is a stick 5 to be pivoted by a stick cylinder 5st, and pivotally supported on a front end portion of this stick 5 is an attachment tool 6 to be pivoted by a bucket cylinder 6bk in place of an original bucket.
The attachment tool 6 includes a type provided with a tool actuator 6at, such as a crusher hydraulic cylinder, that reciprocatively operates upon receiving hydraulic oil fed bidirectionally and a type provided with a tool actuator, such as a hydraulic breaker, that reciprocatively operates by an internal selector valve mechanism upon receiving hydraulic oil fed unidirectionally.
In such a work machine A, for a hydraulic circuit that operates the fluid pressure actuator such as a boom cylinder 4bm, as shown in FIG. 10, feed ports of a control valve 16 are communicated with a drive pump 12 and an idle pump 13 that sucks and discharges hydraulic oil serving as hydraulic fluid in a tank 11 via pump lines 14 and 15, and the control valve 16 is incorporated internally with a travel motor controlling spool, a swing motor controlling spool, boom cylinder controlling spools 16bm and 16bm2, a stick cylinder controlling spool, a bucket cylinder controlling spool, and tool controlling spools 16at1 and 16at2.
The boom cylinder controlling spools 16bm and 16bm2 are both for direction control and speed control of the boom cylinder 4bm, the tool controlling spools 16at1 and 16at2 are both for direction control and speed control of the tool actuator 6at, and these spools are provided two each so as to secure a large flow rate necessary for obtaining a required operation speed.
As shown in FIG. 10 and FIG. 11, the tool actuator 6at is operated by two pumps (drive pump 12 and idle pump 13) in an open-center circuit, even when a boom-up operation of the boom cylinder 4bm is intended, since the boom operating pressure of the boom cylinder 4bm is higher than the tool operating pressure, discharged flows from the drive pump 12 and the idle pump 13 all flow to the tool actuator 6at having a low load pressure, and interlockability between a tool operation and a boom-up operation is lost.
Therefore, even when the tool actuator 6at is operated by two pumps (drive pump 12 and idle pump 13) as shown in FIG. 12 and FIG. 13, for a boom-up operation of the boom cylinder 4bm, a pilot pressure line to one tool controlling spool 16at1 is forcibly controlled, one pump (idle pump 13) is made to operate the tool actuator 6at via the other tool controlling spool 16at2, and the other pump (drive pump 12) is allocated to the boom cylinder 4bm through the boom cylinder controlling spool 16bm, whereby interlockability between the boom cylinder 4bm and the tool actuator 6at is improved.
In this case, by three solenoid selector valves 27s1, 27s2, and 27s3 as shown in FIG. 14 and FIG. 15, four ports of the two tool controlling spools 16at1 and 16at2 are controlled for a change between one pump and two pumps and between a unidirectional feed and a bidirectional feed as shown in the following Table 1. Here, an overall description of the circuit diagram is omitted, as this will be described in detail based on FIG. 1.
TABLE 1Unidirection/1P/2PBidirectionSOL1SOL2SOL3EC1EC2Tool setting1P unidirectional feedxxx∘∘1P bidirectional feedxx∘xx2P unidirectional feed∘∘x∘∘2P bidirectional feed∘∘∘xx
For example, as shown in FIG. 14, in a case of one pump and a bidirectional feed, by turning on the solenoid selector valve 27s3, one tool controlling spool 16at2 is made bidirectionally operable, so that the opening/closing operation-type tool actuator 6at can be operated bidirectionally.
Moreover, as shown in FIG. 15, in a case of two pumps and a unidirectional feed, by turning on the solenoid selector valves 27s1 and 27s2 and turning on solenoid valves 46 and 49 in return passages, both tool controlling spools 16at1 and 16at2 are made unidirectionally operable, so that a large flow rate of hydraulic oil can be fed unidirectionally to the tool actuator 6at such as a hydraulic breaker.